Autonomous driving assistance system, autonomous driving assistance method, and computer program

ABSTRACT

Autonomous driving assistance systems, methods, and programs obtain road information that specifies line types of lane markings and connection types of lanes and specify, when a vehicle travels with autonomous driving assistance, a planned route to be taken by the vehicle based on the road information. The systems, methods, and programs execute the autonomous driving assistance for the vehicle according to the specified planned route.

TECHNICAL FIELD

Related technical fields include autonomous driving assistance systems,methods, and programs which execute autonomous driving assistance forvehicles.

BACKGROUND

In recent years, in addition to manual driving in which a vehicletravels based on user's driving maneuvers, a new drive mode has beenproposed regarding autonomous driving assistance systems that assist theuser in driving a vehicle by performing a part or all of user's drivingmaneuvers by the vehicle. For example, the autonomous driving assistancesystem autonomously performs vehicle control such as control ofsteering, a driving source, and a brake so as to keep the vehicleapproximately centered in the same lane while maintaining a presetvehicle speed and a certain distance to a vehicle ahead. The autonomousdriving assistance system is advantageous in that it eases the drivingburden on the user. However, in order to allow the vehicle toappropriately travel with autonomous driving assistance, it is importantto more quickly and accurately specify a route to be taken by thevehicle.

For example, as shown in FIG. 16, in the case where a straight road 102and a curved road 103 are connected at a branch point ahead of a vehicletraveling on a road 101, control for autonomous driving assistancevaries depending on which way the vehicle is going to go at the branchpoint. That is, in the case where the vehicle is going to take thecurved road 103, the vehicle needs to be decelerated to a speedaccording to the radius of curvature of the curve by the time thevehicle enters the curve. In the case where the vehicle is going to takethe straight road 102, such deceleration is not needed, and it isdesirable that the vehicle travel at as constant a speed as possible soas not to impede traffic flow. Accordingly, appropriate autonomousdriving assistance cannot be executed unless a route to be taken by thevehicle can be specified. For example, International Publication No.2011/158347 (WO 2011/158347) proposes a technique in which, in the casewhere a destination has been set, autonomous driving assistance isexecuted by using a route to the destination as the course of thevehicle, and in the case where no destination has been set, autonomousdriving assistance is executed by using a route along the road as thecourse of the vehicle.

SUMMARY

As used herein, the expression “along the road” basically specifies therelationship between roads. Which road has the relationship of “alongthe road” with which road is basically artificially set by cartographiccompanies that produce map information. Accordingly, in WO 2011/158347,in the case where the straight road 102 has been set to have therelationship of “along the road” with the road 101 and the vehicle istraveling toward the branch shown in FIG. 16 with no destination beingset, autonomous driving assistance is executed based on the presumptionthat the vehicle is going to take the straight road 102 rather than thecurved road 103. In the example shown in FIG. 16, however, the leftmostlane of the road 101 is connected to the curved road 103, and thevehicle is not necessarily going to take the straight road 102.Especially in the case where the vehicle is traveling on the leftmostlane, there is also a high possibility that the vehicle may be going totake the curved road 103. In this case, since the vehicle traveling withautonomous driving assistance is going to make a lane change from theleftmost lane of the road 101 to the straight road 102, the driver needsto perform vehicle maneuvers so that the vehicle does not make a lanechange from the leftmost lane of the road 101 to the straight road 102.That is, in WO 2011/158347, a vehicle's planned route ahead of thevehicle in the direction in which the vehicle is traveling is determinedbased on the relationship of “along the road” between roads which isartificially set by cartographic companies that produce map information,and without using the “line types of lane markings” and the “connectiontypes of lanes” as information specifying classification of lanes ofroads and road connection for each lane. Accordingly, a planned routecannot be appropriately specified.

Exemplary embodiments of the broad inventive principles described hereinprovide an autonomous driving assistance system, an autonomous drivingassistance method, and a computer program, which allow a planned routeto be taken by a vehicle to be specified by using the “line types oflane markings” and the “connection types of lanes” and whichparticularly allow a planned route to be taken by a vehicle to be morequickly and accurately specified as compared to conventional exampleseven when a guidance route has not been set.

Exemplary embodiments provide autonomous driving assistance systems,methods, and programs that obtain road information that specifies linetypes of lane markings and connection types of lanes and specify, when avehicle travels with autonomous driving assistance, a planned route tobe taken by the vehicle based on the road information. The systems,methods, and programs execute the autonomous driving assistance for thevehicle according to the specified planned route.

The term “autonomous driving assistance” refers to the function toperform at least a part of driver's vehicle maneuvers on behalf of thedriver or to assist the driver with at least a part of driver's vehiclemaneuvers.

According to the autonomous driving assistance system, the autonomousdriving assistance method, and the computer program which have the aboveconfiguration, a planned route to be taken by the vehicle can bespecified by using the “line types of lane markings” and the “connectiontypes of lanes.” In particular, even if a guidance route has not beenset, a planned route to be taken by the vehicle can be more quickly andaccurately specified as compared to conventional examples as the plannedroute to be taken by the vehicle is specified based on classification oflanes located ahead in the direction in which the vehicle is travelingand road connection for each lane. This allows the vehicle toappropriately travel with autonomous driving assistance based on thespecified planned route.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of a navigationsystem according to an embodiment.

FIG. 2 is a diagram showing an example of map information of a roadsection which is stored in a map information DB.

FIG. 3 is a diagram showing an example of map information of a roadsection which is stored in the map information DB.

FIG. 4 is a flowchart of an autonomous driving assistance programaccording to an embodiment.

FIG. 5 is a flowchart of the autonomous driving assistance programaccording to the embodiment.

FIG. 6 is a diagram illustrating a method for specifying a planned routein the case where a lane is added and branches off from existing lanes.

FIG. 7 is a diagram illustrating a method for specifying a planned routein the case where a merging point and a branch point are presentsuccessively.

FIG. 8 is a diagram showing an example in which a planned route cannotbe specified based on a lane in which a vehicle is traveling.

FIG. 9 is a diagram showing an example in which a planned route cannotbe specified based on a lane in which a vehicle is traveling.

FIG. 10 is a diagram showing an example in which a planned route can bespecified based on a lane in which a vehicle is traveling.

FIG. 11 is a diagram illustrating a method for specifying a plannedroute based on the relationship of “along the road.”

FIG. 12 is a diagram showing a control intervention monitoring section.

FIG. 13 is a diagram illustrating a modification of the autonomousdriving assistance program.

FIG. 14 is a diagram illustrating the modification of the autonomousdriving assistance program.

FIG. 15 is a diagram illustrating a method for specifying a plannedroute in the case where an existing lane branches off and a lane isadded thereto.

FIG. 16 is a diagram illustrating a conventional problem.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

An autonomous driving assistance system will be described in detailbelow based on an embodiment of a navigation system with reference tothe accompanying drawings. First, the general configuration of anavigation system 1 according to an embodiment will be described withreference to FIG. 1. FIG. 1 is a block diagram of the navigation system1 according to the embodiment.

As shown in FIG. 1, the navigation system 1 according to the embodimentis comprised of: a current position detection unit 11 that detects thecurrent position of a vehicle equipped with the navigation system 1; adata recording unit 12 having various data recorded thereon; anavigation ECU 13 that performs various arithmetic operations based onreceived information; an operation unit 14 that accepts user'soperations; a liquid crystal display 15 that displays to the user a maparound the vehicle, information about a guidance route set by thenavigation system 1, etc.; a speaker 16 that outputs voice guidanceabout the route guidance; a DVD drive 17 that reads a DVD serving as astorage medium; and a communication module 18 that communicates with aninformation center such as a probe center or a Vehicle Information andCommunication System (VICS (registered trademark)) center. (As usedherein, the term “storage medium” is not intended to encompasstransitory signals.) An external camera 19 and various sensors which aremounted on the vehicle equipped with the navigation system 1 areconnected to the navigation system 1 via an in-vehicle network such as aCAN. A vehicle control ECU 20 that performs various controls of thevehicle equipped with the navigation system 1 is also connected to thenavigation system 1 so that the navigation system 1 and the vehiclecontrol ECU 20 can communicate with each other in two ways. Variousoperation buttons 21 mounted on the vehicle, such as an autonomousdriving start button, are also connected to the navigation system 1.

The components of the navigation system 1 will be sequentially describedbelow.

The current position detection unit 11 is comprised of a GPS 22, avehicle speed sensor 23, a steering sensor 24, a gyro sensor 25, etc.and can detect the current position and orientation of the vehicle, thetraveling speed of the vehicle, the current time, etc. In particular,the vehicle speed sensor 23 is a sensor that detects the distancetraveled by the vehicle and the vehicle speed. The vehicle speed sensor23 generates pulses according to rotation of drive wheels of the vehicleand outputs pulse signals to the navigation ECU 13. The navigation ECU13 counts the number of generated pulses to calculate the rotationalspeed of the drive wheels and the traveled distance. The navigationsystem 1 need not necessarily include all of these four sensors. Thenavigation system 1 may include only one or more of these sensors.

The data recording unit 12 includes a hard disk (not shown) serving asan external storage device and a recording medium, and a recording head(not shown) serving as a driver for reading a map information DB 31, apredetermined program, etc. recorded on the hard disk and writingpredetermined data on the hard disk. The data recording unit 12 may becomprised of a flash memory, a memory card, or an optical disk such as aCD or a DVD instead of the hard disk. The map information DB 31 may bestored in an external server, and the navigation system 1 may obtain themap information DB 31 by communication with the external server.

The map information DB 31 is storage means having stored therein, e.g.,link data 34 regarding roads (links), node data 35 regarding nodepoints, search data 36 that is used for processing associated with aroute search and a route change, facility data regarding facilities, mapdisplay data for displaying a map, intersection data regardingintersections, search data for searching for locations, etc.

The link data 34 includes: regarding links of roads, data indicating thewidth, gradient, cant, and bank of the road to which the link belongs,the road surface condition, a merging section, the road structure, thenumber of lanes of the road, a location where the number of lanesdecreases, a location where the road narrows, a railroad crossing, etc.;regarding corners, data indicating the radius of curvature, anintersection, a T-junction, the entrance and exit of the corner, etc.;regarding road attributes, data indicating a downhill road, an uphillroad, etc.; and regarding road types, data indicating a local road suchas a national road, a prefectural road, or a narrow street, and a tollroad such as a national expressway, an urban expressway, an automobileroad, a local toll road, or a toll bridge. In particular, in the presentembodiment, information is also stored which specifies road connectionfor each lane (more specifically, the shapes of a merging point and abranch point, and which lane connects to which road at the merging pointand the branch point) in addition to classification of lanes of roads.

Specifically, the “numbers of lanes,” the “line types of lane markings,”and the “connection types of lanes” are stored in the map information DB31 as the information that specifies classification of lanes of roadsand road connection for each lane. The “numbers of lanes” is informationindicating the number of lanes (e.g., 1, 2, 3, etc.) of each road. The“line types of lane markings” is information indicating the type of eachlane marking (e.g., solid line, dashed line, zebra, etc.). The“connection types of lanes” is information indicating, for each lane,how lanes of each road change (e.g., continue, add, end, divide, andmerge).

“Zebra,” which is a “line type of lane markings,” is a marking that isused at a branch point or a merging point to indicate the start ofmerging or the end of branching of a road and to allow vehicles toappropriately merge or branch off. “Zebra” is slant white lines drawn atpredetermined intervals. An example of “Zebra” is a channelizing strip.“Continue,” which is a “connection type of lanes,” means that the numberof lanes does not increase or decrease. “Add” means that the number oflanes increases. “End” means that the number of lanes decreases.“Divide” means that the number of lanes increases as a single lanedivides into a plurality of lanes. “Merge” means that the number oflanes decreases as a plurality of lanes merge into a single lane. Foreach change point where the lane configuration changes (each locationwhere the number of lanes increases or decreases, each location wherethe line type of lane markings changes, etc.) in a road network in allover the country, information about the “numbers of lanes,” the “linetypes of lane markings,” and the “connection types of lanes” is storedregarding sections at and after the change point.

The navigation ECU 13 can specify classification of lanes of roads androad connection for each lane by obtaining, from the map information DB31, information about the “numbers of lanes,” the “line types of lanemarkings,” and the “connection types of lanes” in the direction in whichthe vehicle is traveling. For example, the number of lane at eachlocation can be specified by the “numbers of lanes.” In addition to asection where a lane merges with another lane and a section where avehicle can make a lane change to an added lane, the boundary between amain road and a merging or added lane (i.e., classification between mainroads and lanes other than the main roads) in the case where a lanemerges into or is added to a main road can be specified by the “linetypes of lane markings.” For each lane, whether a lane is an existinglane that will continue, an added lane, or a lane that will end can bespecified by the “connection types of lanes.”

FIGS. 2 and 3 are diagrams each showing an example of variousinformation of a road section which is stored in the map information DB31. For example, regarding a road section shown in FIG. 2, thenavigation ECU 13 can refer to the information and can specify that anew lane is added to the left of a two-lane main road at a branch pointand that the added lane branches off in a different direction from theother lanes. Regarding a road section shown in FIG. 3, the navigationECU 13 can refer to the information and can specify that a two-lane roadand a single-lane road merge from different directions at a mergingpoint to form a three-lane road section and that the three-lane roadsection divides back into a two-lane road and a single-lane road at abranch point located after the merging point so as to branch indifferent directions.

The node data 35 includes data regarding the coordinates (positions) ofnode points that are set at branch points (including intersections,T-junctions, etc.) of actual roads and that are set at predeterminedintervals on each road according to the radius of curvature etc., nodeattributes indicating whether the node is a node corresponding to anintersection or not etc., a connection link number list that is a listof link numbers of links connecting to the node, an adjacent node numberlist that is a list of node numbers of nodes each located adjacent tothe node with a link therebetween, the height (altitude) of each nodepoint, etc.

The search data 36 includes various data to be used for route searchprocessing of searching for a route from a departure point (e.g., thecurrent position of the vehicle) to a set destination. Specifically,cost calculation data to be used to calculate search cost such as costshowing a quantified level of appropriateness of a route regarding anintersection (hereinafter referred to as intersection cost) and costshowing a quantified level of appropriateness of a route regarding eachlink of a road (hereinafter referred to as link cost) is stored as thesearch data 36.

The navigation electronic control unit (ECU) 13 is an electronic controlunit that generally controls the navigation system 1. The navigation ECU13 includes: a CPU 41 serving as an arithmetic unit and a control unit;and internal storage devices such as a RAM 42 that is used as a workingmemory when the CPU 41 performs various arithmetic operations and thatstores route data etc. when a route search is conducted, a ROM 43 havingrecorded thereon an autonomous driving assistance program (see FIGS. 4and 5) described below etc. in addition to a control program, and aflash memory 44 that stores a program read from the ROM 43. Thenavigation ECU 13 forms various means serving as processing algorithms.For example, planned route specifying means specifies a planned route tobe taken by the vehicle in the case where the vehicle travels withautonomous driving assistance. Vehicle control means executes autonomousdriving assistance for the vehicle according to the planned routespecified by the planned route specifying means. Route determining meansdetermines if a guidance route for guiding the vehicle has been set.Road information obtaining means obtains road information that specifiesclassification of lanes located ahead in the direction in which thevehicle is traveling and road connection for each lane.

The operation unit 14 is operated to enter a departure point as a travelstart point and a destination as a travel end point etc. and is formedby a plurality of operation switches (not shown) such as various keysand buttons. The navigation ECU 13 performs control to execute variousassociated operations based on switch signals output in response todepression etc. of the switches. The operation unit 14 may be formed bya touch panel that is provided on the front surface of the liquidcrystal display 15. Alternatively, the operation unit 14 may be formedby a microphone and a speech recognition device.

A map image including roads, traffic information, operation guidance, anoperation menu, key guidance, guidance information about a guidanceroute, news, a weather forecast, time, emails, TV programs, etc. aredisplayed on the liquid crystal display 15. In the present embodiment,in the case where autonomous driving assistance is started or cancelled,guidance on start or cancellation of autonomous driving assistance isalso displayed on the liquid crystal display 15. An HUD or an HMD may beused instead of the liquid crystal display 15.

The speaker 16 outputs voice guidance on the travel along a guidanceroute or a lane change route 33 and guidance on traffic information,based on commands from the navigation ECU 13. In the present embodiment,in the case where autonomous driving assistance is started or cancelled,the speaker 16 also outputs voice guidance on start or cancellation ofautonomous driving assistance.

Drive modes of the vehicle include traveling with autonomous drivingassistance in which the vehicle autonomously travels along a presetroute or along the road without user's driving maneuvers, in addition tomanual driving in which the vehicle travels based on user's drivingmaneuvers. For example, in driving with autonomous driving assistance,the current position of the vehicle, the current lane of the vehicle,and the position of other traffic around the vehicle are detected asneeded, and the vehicle control ECU 20 autonomously performs vehiclecontrol such as control of steering, a driving source, and a brake sothat the vehicle travels along a preset route or along the road. Inparticular, as described later in the present embodiment, a plannedroute to be taken by the vehicle is specified and the content of controlis set based on the planned route.

Specifically, in the present embodiment, the following five types ofautonomous driving assistance are executed according to the specifiedplanned route.

(1) “Constant speed cruising” . . . . The vehicle is controlled totravel in the same lane at a predetermined set speed (e.g., 90% of thespeed limit of a road on which the vehicle is traveling).

(2) “Adaptive cruising” . . . . The vehicle is controlled to travel inthe same lane at up to a set speed (e.g., 90% of the speed limit of aroad on which the vehicle is traveling) while maintaining a certaindistance (e.g., 10 m) to a vehicle ahead.

(3) “Speed management (curve)” . . . . When there is a curve ahead inthe direction in which the vehicle is traveling, the vehicle isdecelerated to a speed according to the radius of curvature of the curveby the time the vehicle enters the curve.

(4) “Speed management (exit road)” . . . . Acceleration of the vehicleis restrained when the vehicle travels in a deceleration lane (exitroad) of an expressway etc.

(5) “Speed management (tollgate, stop sign, signal)” . . . . When thereis a tollgate, a stop sign, or a signal ahead in the direction in whichthe vehicle is traveling, the vehicle is decelerated to a speed (e.g.,20 km/h) at which the vehicle can be stopped without placing a burden onan occupant of the vehicle by the time the vehicle reaches the tollgate,the stop sign (road sign), or the signal.

The following control is also performed in parallel with the controls(1) to (5).

-   -   (6) Control to keep the vehicle approximately centered in the        lane without causing lane deviation (e.g., lane keeping        assistance).

For example, “constant speed cruising” or “adaptive cruising” isbasically performed in the case where a planned route does not have aspecial road shape such as a curve. Special control according to theroad shape (e.g., “speed management (curve),” “speed management (exitroad),” etc.) is performed in the case where a planned route includes aspecial road shape such as a curve. When traveling with autonomousdriving assistance of the present embodiment, the vehicle is notcontrolled to make lane changes and right and left turns, and thevehicle basically travels in the same lane unless the user performsvehicle maneuvers to change lanes or to turn right or left.

The controls (1) to (6) for autonomous driving assistance may beperformed either in all road sections or only when the vehicle istraveling on a freeway having gates (either manned or unmanned, andeither toll or toll-free) at boundaries with other roads connecting tothe freeway. Autonomous driving assistance is not necessarily executedwhen the vehicle travels in a section where the vehicle can travelautonomously (hereinafter referred to as an autonomous driving section),but is executed only in situations where execution of autonomous drivingassistance is selected by the user and it is determined that the vehiclecan travel with autonomous driving assistance. An example of situationswhere the vehicle cannot travel with autonomous driving assistance is asituation where road information required to execute autonomous drivingassistance, such as lane markings, cannot be obtained.

There are cases where autonomous driving assistance is stopped when itis detected that the user has performed a specific vehicle maneuver ofan accelerator, a brake, steering, etc. (hereinafter referred to as anoverride) while the vehicle is traveling with autonomous drivingassistance. For example, the controls (1) to (5) are stopped when it isdetected that the user has operated a brake. When it is detected thatthe user has performed a steering operation, the controls (1) to (5) arebasically continued, but the control (6) is temporarily stopped untilthe operation is terminated.

The DVD drive 17 is a drive that can read data recorded on a recordingmedium such as a DVD or a CD. The DVD drive 17 plays music or videos,updates the map information DB 31, etc. based on the read data. A cardslot for reading and writing a memory card may be provided instead ofthe DVD drive 17.

The communication module 18 is a communication device that receivestraffic information, probe information, weather information, etc.transmitted from a traffic information center such as, e.g., a VICScenter or a probe center. For example, the communication module 18 is amobile phone or a DCM. Other examples of the communication module 18include a vehicle-to-vehicle communication device for communicationbetween vehicles, and a roadside-to-vehicle communication device forcommunication between a vehicle and a roadside unit.

The external camera 19 is, e.g., a camera using a solid state imagingelement such as a CCD. The external camera 19 is attached to the vehicleat a position above a front bumper and is mounted such that its opticalaxis is tilted downward at a predetermined angle with respect to thehorizontal direction. The external camera 19 captures an image of theroad ahead in the direction in which the vehicle is traveling, when thevehicle travels in an autonomous driving section. The vehicle controlECU 20 processes the captured image to detect pavement markings on theroad on which the vehicle is traveling, other traffic around thevehicle, etc. and performs autonomous driving assistance for the vehiclebased on the detection result. The external camera 19 may be placed onthe rear or side part of the vehicle instead of on the front part of thevehicle. Instead of the camera, a sensor such as a millimeter waveradar, vehicle-to-vehicle communication, or roadside-to-vehiclecommunication may be used as means for detecting other traffic. Anilluminance sensor or a rain sensor may be mounted as means fordetecting other surrounding environments.

The vehicle control ECU 20 is an electronic control unit that controlsthe vehicle equipped with the navigation system 1. The vehicle controlECU 20 is connected to each driving part of the vehicle such assteering, a brake, and an accelerator. In the present embodiment, thevehicle control ECU 20 executes autonomous driving assistance for thevehicle by controlling each driving part particularly after autonomousdriving assistance is started in the vehicle. When the user performs anoverride during autonomous driving assistance, the vehicle control ECU20 detects the override.

The navigation ECU 13 sends command signals regarding autonomous drivingassistance to the vehicle control ECU 20 via a CAN after the vehiclestarts to travel. The vehicle control ECU 20 executes autonomous drivingassistance after the vehicle starts to travel, in response to thereceived command signals. The command signals contain information aboutthe content of control for autonomous driving assistance (e.g., any ofthe controls (1) to (6)) to be executed on the vehicle and informationinstructing to start, stop, or change the control etc. Instead of thenavigation ECU 13, the vehicle control ECU 20 may set the content ofcontrol for autonomous driving assistance. In that case, the vehiclecontrol ECU 20 is configured to obtain information required to set thecontent of control for autonomous driving assistance, such as a guidanceroute, the condition of the vehicle, and map information of surroundingareas, from the navigation system 1.

The autonomous driving assistance program that is executed by the CPU 41in the navigation system 1 of the present embodiment having the aboveconfiguration will be described below based on FIGS. 4 and 5. FIGS. 4and 5 are flowcharts of the autonomous driving assistance programaccording to the present embodiment. The autonomous driving assistanceprogram is a program that is executed after an ACC power of the vehicleis turned on and that specifies a planned route to be taken by thevehicle and executes autonomous driving assistance based on thespecified planned route. The autonomous driving assistance program maybe executed only when autonomous driving assistance is being executed inthe vehicle or may also be executed when the vehicle is traveling bymanual driving. The program shown by the flowcharts of FIGS. 4 and 5 isstored in the RAM 42 or the ROM 43 of the navigation system 1 and isexecuted by the CPU 41.

An example in which the vehicle is traveling particularly in a main roadof a freeway will be described below.

In the autonomous driving assistance program, the CPU 41 first obtains,in step (hereinafter abbreviated as S) 1, the current position of thevehicle detected by the current position detection unit 11. It isdesirable that the current position of the vehicle be specified indetail by using high accuracy location technology. The high accuracylocation technology is technology that enables the lane in which avehicle is traveling and the accurate position of the vehicle to bedetected by detecting, by image recognition, white lines and roadsurface paint information obtained from a camera mounted on the vehicleand checking the white lines and the road surface paint information witha pre-stored map information DB. Since details of the high accuracylocation technology are known in the art, description thereof will beomitted. In the case where the vehicle is traveling on a road having aplurality of lanes, the lane in which the vehicle is traveling is alsospecified in S1.

Subsequently, in S2, the CPU 41 obtains from the map information DB 31road information ahead in the direction in which the vehicle istraveling. The road information obtained in S2 includes informationspecifying the positions of branch points where a single route dividesinto a plurality of routes and merging points where a plurality ofroutes merges into a single route.

Subsequently, in S3, the CPU 41 determines based on the informationobtained in S1 and S2 if there is any merging point within apredetermined distance (e.g., within 3 km) in the opposite directionthat the vehicle is traveling.

If it is determined that there is a merging point within thepredetermined distance in the opposite direction that the vehicle istraveling (S3: YES), the routine proceeds to S4. If it is determinedthat there is no merging point within the predetermined distance in theopposite direction that the vehicle is traveling (S3: NO), the routineproceeds to S5.

In S4, the CPU 41 specifies from the map information stored in the mapinformation DB 31 classification of lanes of roads and road connectionfor each lane at the merging point determined to be present within thepredetermined distance behind the vehicle in S3 (more specifically, theshape of the merging point and which lane is connected to which road atthe merging point). As described above, the map information DB 31 hasstored therein the “numbers of lanes,” the “line types of lanemarkings,” and the “connection types of lanes,” and the CPU 41specifies, based on the information stored in the map information DB 31,classification of lanes of roads and road connection for each lane atthe merging point (FIGS. 2 and 3).

Subsequently, in S5, the CPU 41 determines based on the informationobtained in S1 and S2 if there is any branch point within apredetermined distance (e.g., within 3 km) ahead in the direction inwhich the vehicle is traveling.

If it is determined that there is a branch point within thepredetermined distance ahead in the direction in which the vehicle istraveling (S5: YES), the routine proceeds to S6. If it is determinedthat there is no branch point within the predetermined distance ahead inthe direction in which the vehicle is traveling (S5: NO), the routineproceeds to S7.

In S6, the CPU 41 specifies from the map information stored in the mapinformation DB 31 classification of lanes of roads and road connectionfor each lane at the branch point determined to be present within thepredetermined distance ahead in S5 (more specifically, the shape of thebranch point and which lane is connected to which road at the branchpoint). As described above, the map information DB 31 has stored thereinthe “numbers of lanes,” the “line types of lane markings,” and the“connection types of lanes,” and the CPU 41 specifies, based on theinformation stored in the map information DB 31, classification of lanesof roads and road connection for each lane at the branch point (FIGS. 2and 3). The routine then proceeds to S8.

In S7, the CPU 41 determines that, since there is no branch point aheadin the direction in which the vehicle is traveling, a route to be takenby the vehicle should be necessarily only one route along the directionin which the vehicle is currently traveling. The CPU 41 thus specifiesthe route along the direction in which the vehicle is currentlytraveling as a planned route. The routine then proceeds to S19.

In S8, the CPU 41 determines if a guidance route has been set in thenavigation system 1. For example, if the user sets a destination whenthe vehicle starts to travel, route search processing is performed byusing known Dijkstra's algorithm, and a guidance route is set from aplurality of candidates by user's operation.

If it is determined that a guidance route has been set in the navigationsystem 1 (S8: YES), the routine proceeds to S9. If it is determined thata guidance route has not been set in the navigation system 1 (S8: NO),the routine proceeds to S10.

In S9, the CPU 41 determines that, since a guidance route has been setin the navigation system 1, the vehicle is going to travel along the setguidance route. The CPU 41 thus specifies a route along the guidanceroute as a planned route. The routine then proceeds to S19.

In S10, the CPU 41 determines, based on the information about the branchpoint obtained in S6, if a new lane added at the branch point determinedto be present within the predetermined distance ahead in S5 becomes aroute different from an existing lane (that is, a lane of a main road inwhich the vehicle is traveling) at this branch point. Specifically, thiscorresponds to the case where a new lane 53 is added to existing lanes51, 52 at a position ahead in the direction in which a vehicle 50 istraveling so that the new lane 53 branches off from the existing lanes51, 52, as shown in FIG. 6.

If it is determined that a new lane added at the branch point determinedto be present within the predetermined distance ahead becomes a routedifferent from an existing lane at this branch point (S10: YES), theroutine proceeds to S11. If it is determined that a new lane added atthe branch point determined to be present within the predetermineddistance ahead does not become a route different from an existing laneat this branch point (S10: NO), the routine proceeds to S12.

In S1, the CPU 41 determines that, as a route that is to be taken by thevehicle on the presumption that the vehicle travels without changinglanes, a single route can be specified based only on the roadinformation. The single route thus specified is used as a planned route.Specifically, a route along a lane in which the vehicle is currentlytraveling is specified as a planned route. For example, in the casewhere the new lane 53 is added to the existing lanes 51, 52 at aposition ahead in the direction in which the vehicle 50 is traveling sothat the new lane 53 branches off from the existing lanes 51, 52 asshown in FIG. 6, there are two possible routes to be taken by thevehicle, namely a route along the existing lanes 51, 52 and a routealong the lane 53, and the route along the existing lanes 51, 52 isspecified as a planned route. The routine then proceeds to S19.

When traveling with autonomous driving assistance of the presentembodiment, the vehicle does not autonomously make lane changes, asdescribed above. Accordingly, the vehicle continues to travel in thesame lane as the lane in which the vehicle is currently traveling unlessthe user intentionally performs a steering operation. A planned routecan thus be specified as described above in S11 or as described below inS17. If the user performs a steering operation to change lanes, theplanned route is cancelled as described below, and a planned route isspecified again based on the new position of the vehicle (S22).Accordingly, for example, in the case where the vehicle 50 changes lanesto the new lane 53 in the situation shown in FIG. 6, the planned routealong the lanes 51, 52 is cancelled, and a new planned route along thelane 53 is specified.

In S12, the CPU 41 determines, based on the information about themerging point obtained in S4 and the information about the branch pointobtained in S6, if there is a merging point within the predetermineddistance in the opposite direction that the vehicle is traveling, and ifa new lane added at the merging point does not end but becomes a routedifferent from an existing lane (that is, a lane of a main road in whichthe vehicle is traveling) at the branch point determined to be presentwithin the predetermined distance ahead in S5. Specifically, thiscorresponds to the case where a merging point where a new lane 57 mergesto existing lanes 55, 56 is present in the opposite direction that thevehicle 50 is traveling, and the lane 57 does not end but continues andbranches off from the existing lanes 55, 56 in a different direction atthe branch point that is present ahead in the direction in which thevehicle 50 is traveling, as shown in FIG. 7.

If it is determined that there is a merging point within thepredetermined distance in the opposite direction that the vehicle istraveling and that a new lane added at the merging point does not endbut becomes a route different from an existing lane at the branch pointdetermined to be present within the predetermined distance ahead (S12:YES), the routine proceeds to S13. If it is determined that there is nomerging point within the predetermined distance in the oppositedirection that the vehicle is traveling, or even if there is a mergingpoint, if it is determined that a new lane added at the merging point isnot such a lane that does not end but becomes a route different from anexisting lane at the branch point determined to be present within thepredetermined distance ahead (S12: NO), the routine proceeds to S15.

In S13, the CPU 41 determines, based on the travel history of thevehicle, if the direction in which the vehicle merged at the mergingpoint determined to be present within the predetermined distance in theopposite direction that the vehicle is traveling in S12 has been able tobe specified. For example, in the example shown in FIG. 7, the vehiclecan merge in the following two directions at the merging point, namelythe direction X in which the vehicle merges from the lane 55, 56 of themain road and the direction Y in which the vehicle merges from the lane57 other than the main road.

If it is determined that the direction in which the vehicle merged atthe merging point has been able to be specified (S13: YES), the routineproceeds to S14. If it is determined that the direction in which thevehicle merged at the merging point has not been able to be specified(S13: NO), the routine proceeds to S15.

In S14, the CPU 41 specifies a lane in which the vehicle is traveling,based on the direction in which the vehicle merged at the merging pointdetermined to be present within the predetermined distance in theopposite direction that the vehicle is traveling. In the case where theCPU 41 cannot specify a single lane as a lane in which the vehicle istraveling, it specifies each candidate lane. When traveling withautonomous driving assistance of the present embodiment, the vehicledoes not autonomously make lane changes, as described above.Accordingly, the vehicle continues to travel in the lane correspondingto the direction in which the vehicle merged unless the userintentionally performs a steering operation. The lane in which thevehicle is currently traveling can thus be specified. For example, inthe example shown in FIG. 7, in the case where the vehicle merged in thedirection X, it can be specified that the vehicle is traveling in one ofthe lanes 55, 56 of the main road. In the case where the vehicle mergedin the direction Y, it can be specified that the vehicle is traveling inthe lane 57. The routine then proceeds to S16.

In S15, the CPU 41 specifies a lane in which the vehicle is traveling,based on the detection result of the current position detected withdetection devices (the GPS 22, the gyro sensor 25, the external camera19, etc.) in S1. As described above, not only the current position(latitude and longitude) of the vehicle but also the lane in which thevehicle is traveling can be specified by using the high accuracylocation technology. In the case where the CPU 41 cannot specify asingle lane as a lane in which the vehicle is traveling, it specifieseach candidate lane.

Subsequently, in S16, the CPU 41 determines if the vehicle's lanespecified in S14 or S15 branches in a plurality of directions at thebranch point located ahead in the direction in which the vehicle istraveling. If a single lane has been able to be specified as a lane inwhich the vehicle is traveling in S14 or S15, it is determined that thelane in which the vehicle is traveling branches in a plurality ofdirections at the branch point, in the case where a lane 60 specified asa lane in which the vehicle 50 is traveling branches in a plurality ofdirections at the branch point without being divided by lane markings asshown in FIG. 8. If a plurality of candidate lanes have been specifiedas a lane in which the vehicle is traveling in S14 or S15, it isdetermined that the lane in which the vehicle is traveling branches in aplurality of directions at the branch point, not only in the case whereat least one of the candidate lanes branches in a plurality ofdirections at the branch point without being divided by lane markings asshown in FIG. 8 but also in the case where a plurality of candidatelanes 61, 62 branch off from each other in different directions as shownin FIG. 9.

Even if a single lane has not been specified as a lane in which thevehicle is traveling in S14 or S15 and there are a plurality ofcandidate lanes, it is determined that the lane in which the vehicle istraveling does not branch in a plurality of directions at the branchpoint, in the case where both candidate lanes 63, 64 branch off in thesame direction at the branch point as shown in FIG. 10, namely in thecase where the route to be taken by the vehicle 50 is the sameregardless of whether the vehicle 50 continues to travel in thecandidate lane 63 or 64.

If it is determined that the lane in which the vehicle is travelingbranches in a plurality of directions at the branch point located aheadin the direction in which the vehicle is traveling (S16: YES), theroutine proceeds to S18. If it is determined that the lane in which thevehicle is traveling does not branch in a plurality of directions at thebranch point located ahead in the direction in which the vehicle istraveling (S16: NO), the routine proceeds to S17.

In S17, the CPU 41 determines that, as a route that is to be taken bythe vehicle on the presumption that the vehicle travels without changinglanes, a single route cannot be specified based only on the roadinformation but can be specified by specifying a lane in which thevehicle is traveling and presuming that the vehicle continues to travelin the specified lane. A route along the lane in which the vehicle iscurrently traveling is thus used as a planned route. For example, in thecase where it is specified that the vehicle 50 is traveling in eitherthe lane 63 or 64 as shown in FIG. 10, a route along the lane 63, 64 isspecified as a planned route. The routine then proceeds to S19.

In S18, the CPU 41 determines that, as a route that is to be taken bythe vehicle on the presumption that the vehicle travels without changinglanes, a single route can be specified neither based only on the roadinformation nor by specifying a lane in which the vehicle is travelingand presuming that the vehicle continues to travel in the specifiedlane. Accordingly, the CPU 41 obtains, from the map information DB 31 orthe external server, information specifying the relationship of “alongthe road” between the roads, and specifies as a planned route a routegoing along the road of the route along which the vehicle is currentlytraveling. For example, in the case where it is specified that thevehicle 50 is traveling in a lane 65 and it is determined that the lane65 branches in a plurality of directions at the branch point withoutbeing divided by lane markings as shown in FIG. 11, the CPU 41 cannotspecify if the vehicle is going to travel straight, or obliquely to theleft, at the branch point. Accordingly, the CPU 41 obtains informationspecifying the relationship of “along the road.” In the case where thevehicle is going to travel straight if it travels along the road, thevehicle is likely to take such a route that the vehicle travels straightat the branch point. The CPU 41 therefore specifies this route as aplanned route. The routine then proceeds to S19.

In S19, the CPU 41 determines if the distance of the planned routespecified in S7, S9, S11, S17, or S18 meets a distance required toexecute autonomous driving assistance. The “distance required to executeautonomous driving assistance” may be a fixed value (e.g., 300 m) or mayvary depending on the type of autonomous driving assistance to beexecuted. For example, for “speed management (curve)” that requires morecomplicated control according to the road shape, the “distance requiredto execute autonomous driving assistance” may be set to a larger valuethan “constant speed cruising” and “adaptive cruising.”

If it is determined that the distance of the planned route specified inS7, S9, S11, S17, or S18 meets the distance required to executeautonomous driving assistance (S19: YES), the routine proceeds to S20.If it is determined that the distance of the planned route specified inS7, S9, S11, S17, or S18 does not meet the distance required to executeautonomous driving assistance (S19: NO), the routine returns to S2, andthe CPU 41 specifies a planned route in a section farther away from thevehicle.

In S20, the CPU 41 together with the vehicle control ECU 20 executesautonomous driving assistance based on the specified planned route.Specifically, autonomous driving assistance is switched as appropriateamong (1) to (6) and executed according to the road shape and the roadtype of the planned route, features that are present on the route, etc.For example, in the case where the planned route has a straight shape,“constant speed cruising” or “adaptive cruising” is performed. In thecase where the planned route has a curved shape, “speed management(curve)” is performed in preparation for the upcoming curve. In the casewhere the planned route includes a tollgate, a stop sign, or a signal,“speed management (tollgate, stop sign, signal)” is performed inpreparation for passing through the tollgate, the stop sign, or thesignal.

Subsequently, in S21, the CPU 41 determines based on the detectionresult of an override maneuver detected by the vehicle control ECU 20if, of overrides, a vehicle maneuver for changing lanes has beenperformed in a control intervention monitoring section. For example, asteering operation to a predetermined angle or more corresponds to thevehicle maneuver for changing lanes.

The control intervention monitoring section is a section where there isa possibility that a planned route may be changed due to a lane change.The control intervention monitoring section is specified based onvarious information about the “numbers of lanes,” the “line types oflane markings,” and the “connection types of lanes” (FIGS. 2 and 3)obtained from the map information DB 31. For example, in the case wherea new lane 73 is added to existing lanes 71, 72 at a position ahead inthe direction in which the vehicle 50 is traveling so that the new lane73 branches off from the existing lanes 71, 72 as shown in FIG. 12, aroute along the existing lanes 51, 52 is a possible route to be taken bythe vehicle as described above, and is specified as a planned route(S11). However, if the vehicle 50 changes lanes from the lane 71, 72 tothe lane 73, the vehicle 50 travels in the lane 73 and a planned routetherefore needs to be changed. Accordingly, a section where the vehiclecan change lanes from the lane 71, 72 to the lane 73 is a controlintervention monitoring section.

If it is determined that a vehicle maneuver for changing lanes has beenperformed in a control intervention monitoring section (S21: YES), a newplanned route needs to be specified, and the routine proceeds to S22. Ifit is determined that a vehicle maneuver for changing lanes has not beenperformed in a control intervention monitoring section (S21: NO), theroutine proceeds to S23.

In S22, the CPU 41 cancels the currently specified planned route. Theroutine then returns to S1 and the CPU 41 specifies a planned routeagain based on the new position of the vehicle, namely the vehicleposition after the vehicle maneuver. However, in the case where aguidance route has been set in the navigation system 1 and a route alongthe guidance route has been specified as a planned route (S9), theplanned route is reliable. Accordingly, the CPU 41 may not cancel theplanned route just by detecting a steering operation in a controlintervention monitoring section. Even in this case, however, the CPU 41may cancel the planned route if the vehicle has deviated from theplanned route (S23: YES).

Subsequently, in S23, the CPU 41 compares the current position of thevehicle with the currently specified planned route and determines if thevehicle has deviated from the planned route.

If it is determined that the vehicle has deviated from the planned route(S23: YES), a new planned route needs to be specified, and the routineproceeds to S22. If it is determined that the vehicle has not deviatedfrom the planned route (S23: NO), it is presumed that the currentplanned route need not be changed, and the routine proceeds to S24.

In S24, the CPU 41 obtains the control state of autonomous drivingassistance by communication with the vehicle control ECU 20 via the CANand determines if the vehicle has terminated autonomous drivingassistance. For example, autonomous driving assistance is terminatedwhen the ACC power is turned off, when the user selects to terminateautonomous driving assistance by performing an operation of the variousoperation buttons 21 mounted on the vehicle such as the autonomousdriving start button, when a specific override such as a brake operationis detected, or when the vehicle enters a road section where autonomousdriving assistance cannot be executed (e.g., a section where lanemarkings cannot be recognized).

If it is determined that the vehicle has terminated autonomous drivingassistance (S24: YES), the autonomous driving assistance program isterminated. If it is determined that the vehicle is still executingautonomous driving assistance (S24: NO), the routine returns to S20.

As described in detail above, in the navigation system 1 according tothe present embodiment, the autonomous driving assistance method that isperformed by the navigation system 1, and the computer program that isexecuted by the navigation system 1, in the case where a vehicle travelswith autonomous driving assistance, it is determined if a guidance routefor guiding the vehicle has been set in the navigation system 1 (S8). Ifit is determined that a guidance route has been set, a route along theguidance route is specified as a planned route (S9). If it is determinedthat a guidance route has not been set, a planned route is specifiedbased on the road information that specifies classification of laneslocated ahead in the direction in which the vehicle is traveling androad connection for each lane (S11, S17, S18), and autonomous drivingassistance for the vehicle is executed according to the specifiedplanned route (S20). A planned route to be taken by the vehicle can thusbe specified by using the “line types of lane markings” and the“connection types of lanes.” In particular, even if a guidance route hasnot been set in the navigation system 1, a planned route to be taken bythe vehicle can be more quickly and accurately specified as compared toconventional examples as the planned route to be taken by the vehicle isspecified based on classification of lanes located ahead in thedirection in which the vehicle is traveling and road connection for eachlane. This allows the vehicle to appropriately travel with autonomousdriving assistance based on the specified planned route.

Various improvements and modifications can be made in other embodimentswithout departing from the spirit and scope of the above embodiment.

For example, the autonomous driving assistance program (FIGS. 4 and 5)that is executed by the CPU 41 in the navigation system 1 according tothe present embodiment may be configured as follows. FIGS. 13 and 14 arediagrams showing a modification of the autonomous driving assistanceprogram according to the present embodiment.

Since the processing of S31 to S35 is similar to that of S1 to S5described above, description thereof will be omitted.

First, in S36, the CPU 41 obtains, from the map information stored inthe map information DB 31, the “line types of lane markings” at thebranch point as one piece of information that specifies classificationof lanes of the road and road connection for each lane at the branchpoint determined to be present within the predetermined distance aheadin S35. As described above, the map information DB 31 has stored thereinthe “numbers of lanes,” the “line types of lane markings,” and the“connection types of lanes” (FIGS. 2 and 3).

Subsequently, in S37, the CPU 41 obtains, from the map informationstored in the map information DB 31, the “connection types of lanes” ofthe road located before (i.e., on the vehicle side of) the branch pointas one piece of information that specifies classification of lanes ofthe road and road connection for each lane at the branch pointdetermined to be present within the predetermined distance ahead in S35.The routine then proceeds to S39.

In S38, the CPU 41 determines that, since there is no branch point aheadin the direction in which the vehicle is traveling, a route to be takenby the vehicle should be necessarily only one route along the directionin which the vehicle is currently traveling. The CPU 41 thus specifiesthe route along the direction in which the vehicle is currentlytraveling as a planned route. The routine then proceeds to S41.

In S39, the CPU 41 determines if a guidance route has been set in thenavigation system 1. For example, if the user sets a destination whenthe vehicle starts to travel, route search processing is performed byusing known Dijkstra's algorithm, and a guidance route is set from aplurality of candidates by user's operation.

If it is determined that a guidance route has been set in the navigationsystem 1 (S39: YES), the routine proceeds to S40. If it is determinedthat a guidance route has not been set in the navigation system 1 (S39:NO), the routine proceeds to S47.

In S40, the CPU 41 determines that, since a guidance route has been setin the navigation system 1, the vehicle is going to travel along the setguidance route. The CPU 41 thus specifies a route along the guidanceroute as a planned route. The routine then proceeds to S41.

Since the subsequent processing of S41 to S46 is similar to that of S19to S24 described above, description thereof will be omitted.

In S47, the CPU 41 determines, based on the information about the “linetypes of lane markings” at the branch point obtained in S36 and the“connection types of lanes” of the road located before (i.e., on thevehicle side of) the branch point obtained in S37, if there is at leastone “zebra” in the “line types of lane markings” at the branch point andif a lane next to the lane marking of “zebra” is “add.” Specifically,this corresponds to the case where existing lanes 75 to 77 branch and anew lane 78 is added next to the lane 77 that branches off from thelanes 75, 76 as shown in FIG. 15, in addition to the case where the newlane 53 is added to the existing lanes 51, 52 at a position ahead in thedirection in which the vehicle 50 is traveling so that the new lane 53branches off from the existing lanes 51, 52 as shown in FIG. 6.

If it is determined that there is at least one “zebra” in the “linetypes of lane markings” at the branch point and a lane next to the lanemarking of “zebra” is “add” (S47: YES), the routine proceeds to S48. Ifit is determined that there is no “zebra” in the “line types of lanemarkings” at the branch point, or even if there is any “zebra,” if it isdetermined that a lane next to the lane marking of “zebra” is not “add”(S47: NO), the routine proceeds to S50.

In S48, the CPU 41 determines if all lanes located either on the rightor on the left of the lane for which the “connection type of lane” hasbeen determined to be “add” in S47 are “add.”

If it is determined that all lanes located either on the right or on theleft of the lane for which the “connection type of lane” has beendetermined to be “add” in S47 are “add” (S48: YES), that is, if noexisting lane branches and a lane is added as shown in FIG. 6, theroutine proceeds to S49. If it is determined that lanes located eitheron the right or on the left of the lane for which the “connection typeof lane” has been determined to be “add” in S47 include a lane otherthan “add” (S48: NO), that is, if an existing lane branches and a laneis added as shown in FIG. 15, the routine proceeds to S51.

In S49, the CPU 41 determines that, as a route that is to be taken bythe vehicle on the presumption that the vehicle travels without changinglanes, a single route can be specified based only on the roadinformation. The single route thus specified is used as a planned route.Specifically, a route along a lane in which the vehicle is currentlytraveling is specified as a planned route. For example, in the casewhere the new lane 53 is added to the existing lanes 51, 52 at aposition ahead in the direction in which the vehicle 50 is traveling sothat the new lane 53 branches off from the existing lanes 51, 52 asshown in FIG. 6, there are possible routes to be taken by the vehicle,namely a route along the existing lanes 51, 52 and a route along thelane 53, and the route along the existing lanes 51, 52 is specified as aplanned route. The routine then proceeds to S41.

In S50, the CPU 41 determines, based on the information about the “linetypes of lane markings” at the branch point obtained in S36 and the“connection types of lanes” of the road located before (i.e., on thevehicle side of) the branch point obtained in S37, if there is at leastone “zebra” in the “line types of lane markings” at the branch point andif a lane next to the lane marking of “zebra” is “continue.”Specifically, this corresponds to the case where the existing lanes 55to 57 branch at the branch point located ahead in the direction in whichthe vehicle 50 is traveling, as shown in FIG. 7.

If it is determined that there is at least one “zebra” in the “linetypes of lane markings” at the branch point and a lane next to the lanemarking of “zebra” is “continue” (S50: YES), the routine proceeds toS51. If it is determined that there is no “zebra” in the “line types oflane markings” at the branch point, or even if there is any “zebra,” ifit is determined that a lane next to the lane marking of “zebra” is not“continue” (S50: NO), the routine proceeds to S53.

Subsequently, in S51, the CPU 41 determines if a lane in which thevehicle is traveling has been able to be specified. As described above,in the case where there is a merging point before the branch point andthe direction in which the vehicle merged at the merging point can bespecified, a lane in which the vehicle is traveling is specified basedon the direction in which the vehicle merged at the merging point (S14).Alternatively, a lane in which the vehicle is traveling may be specifiedbased on the detection result of the current position detected with thedetection devices (the GPS 22, the gyro sensor 25, the external camera19, etc.) in S31 (S15).

If it is determined that a lane in which the vehicle is traveling hasbeen able to be specified by any of the above methods (S51: YES), theroutine proceeds to S52. If it is determined that a lane in which thevehicle is traveling has not been able to be specified (S51: NO), theroutine proceeds to S54.

In S52, the CPU 41 determines, based on the information about the “linetypes of lane markings” at the branch point obtained in S36 and the“connection types of lanes” of the road located before (i.e., on thevehicle side of) the branch point obtained in S37, if the lane in whichthe vehicle is traveling does not divide at the branch point like thelane 60 in FIG. 8 but branches off at the branch point (that is, if thelane in which the vehicle is traveling corresponds to one direction,namely the direction in which the lane branches off at the branchpoint).

If it is determined that the lane in which the vehicle is traveling doesnot divide but branches off at the branch point (S52: YES), it isdetermined that a single route cannot be specified based only on theroad information, but can be specified as a route to be taken by thevehicle by specifying a lane in which the vehicle is traveling andpresuming that the vehicle continues to travel in the specified lane. Aroute along the lane in which the vehicle is currently traveling is thusused as a planned route. For example, in the case where it is specifiedthat the vehicle 50 is traveling in either the lane 63 or 64 as shown inFIG. 10, a route along the lane 63, 64 is specified as a planned route.The routine then proceeds to S41.

If it is determined that the lane in which the vehicle is travelingdivides etc. and that a single route cannot be specified as a route tobe taken by the vehicle even if the lane in which the vehicle istraveling has been specified (S52: NO), the routine proceeds to S54.

In S53, the CPU 41 determines, based on the information about the “linetypes of lane markings” at the branch point obtained in S36 and the“connection types of lanes” of the road located before (i.e., on thevehicle side of) the branch point obtained in S37, if there is at leastone “zebra” in the “line types of lane markings” at the branch point andif all lanes located in the branching direction with respect to the lanemarking of “zebra” are “divide.”

If it is determined that there is at least one “zebra” in the “linetypes of lane markings” at the branch point and all lanes located in thebranching direction with respect to the lane marking of “zebra” are“divide” (S53: YES), the routine proceeds to S54. If it is determinedthat there is no “zebra” in the “line types of lane markings” at thebranch point, or even if there is any “zebra,” if it is determined thatall lanes located in the branching direction with respect to the lanemarking of “zebra” are not “divide” (S53: NO), the routine proceeds toS51.

In S54, the CPU 41 determines that a single route cannot be specified,based only on the road information, as a route that is to be taken bythe vehicle on the presumption that the vehicle travels without changinglanes, and that a route to be taken by the vehicle cannot be specifiedsince a lane in which the vehicle is traveling cannot be specified orthat a route to be taken by the vehicle cannot be specified even if alane in which the vehicle is traveling is specified. Accordingly, theCPU 41 obtains, from the map information DB 31 or the external server,information specifying the relationship of “along the road” between theroads, and specifies as a planned route a route going along the road ofthe route along which the vehicle is currently traveling. For example,in the case where existing lanes branch off and a lane in which thevehicle 50 is traveling cannot be specified as shown in FIG. 10, or inthe case where it is specified that the vehicle 50 is traveling in thelane 65 and it is determined that the lane 65 branches (divides) in aplurality of directions at the branch point without being divided bylane markings as shown in FIG. 11, the CPU 41 cannot specify if thevehicle is going to travel straight, or obliquely to the left, at thebranch point. Accordingly, the CPU 41 obtains information specifying therelationship of “along the road.” In the case where the vehicle is goingto travel straight if it travels along the road, the vehicle is likelyto take such a route that the vehicle travels straight at the branchpoint. The CPU 41 therefore specifies this route as a planned route. Theroutine then proceeds to S41.

In the embodiment, the user manually makes lane changes even whenautonomous driving assistance is being executed. However, lane changesmay be autonomously made with autonomous driving assistance. Makingright and left turns, stopping, starting, etc. may also be autonomouslyperformed with autonomous driving assistance.

In the embodiment, a method for specifying a planned route is describedwith respect to an example in which a vehicle is traveling particularlyon a main road of a freeway. However, even when the vehicle is travelingon a road other than a main road of a freeway or on a local road, aplanned route to be taken by the vehicle can be specified by executingthe autonomous driving assistance program (FIGS. 4 and 5) to obtain roadinformation and specify a lane in which the vehicle is traveling.

In the embodiment, a planned route is specified only when autonomousdriving assistance is being executed. However, a planned route may bespecified even when the vehicle is traveling by manual driving. Thisallows autonomous driving assistance to be appropriately executedaccording to a planned route specified in advance, even immediatelyafter the vehicle is switched from traveling by manual driving totraveling with autonomous driving assistance.

In the embodiment, controlling all of an accelerator operation, a brakeoperation, and a steering wheel operation, which are maneuvers relatedto the vehicle behavior out of vehicle maneuvers, by the vehicle controlECU 20 is described as autonomous driving assistance that is executed sothat the vehicle travels autonomously without user's driving maneuvers.In the autonomous driving assistance, however, the vehicle control ECU20 may control at least one of the accelerator operation, the brakeoperation, and the steering wheel operation, which are the maneuversrelated to the vehicle behavior out of the vehicle maneuvers. Manualdriving based on user's driving maneuvers is described as driving inwhich the user performs all of the accelerator operation, the brakeoperation, and the steering wheel operation, which are the maneuversrelated to the vehicle behavior out of the vehicle maneuvers.

In the embodiment, the navigation system 1 executes the autonomousdriving assistance program (FIGS. 4 and 5). However, the vehicle controlECU 20 may execute the autonomous driving assistance program. In thatcase, the vehicle control ECU 20 obtains the current position of thevehicle, map information, etc. from the navigation system 1.

Devices having a route search function can replace the navigation system1 in other embodiments. For example, embodiments may include to mobilephones, smartphones, tablet computers, personal computers, etc.(hereinafter referred to as the “mobile terminals etc.”). Embodimentsmay include systems formed by a server and a mobile terminal etc. Inthat case, each step of the above autonomous driving assistance program(FIGS. 4 and 5) may be performed by the server and any of the mobileterminal etc. In an embodiment utilizing a mobile terminal etc., avehicle capable of executing autonomous driving assistance and themobile terminal etc. need to be connected (either wired or wireless) sothat they can communicate with each other.

Although the embodiment of the autonomous driving assistance system isdescribed above, the autonomous driving assistance system may have thefollowing configurations. In that case, the autonomous drivingassistance system has the following effects.

For example, a first configuration is as follows.

An autonomous driving assistance system includes: road informationobtaining means for obtaining road information that specifies line typesof lane markings and connection types of lanes; planned route specifyingmeans for specifying, when a vehicle travels with autonomous drivingassistance, a planned route to be taken by the vehicle based on the roadinformation; and vehicle control means for executing the autonomousdriving assistance for the vehicle according to the planned routespecified by the planned route specifying means.

According to the autonomous driving assistance system having the aboveconfiguration, a planned route to be taken by the vehicle can bespecified by using the “line types of lane markings” and the “connectiontypes of lanes.” In particular, even if a guidance route has not beenset, a planned route to be taken by the vehicle can be more quickly andaccurately specified as compared to conventional examples as the plannedroute to be taken by the vehicle is specified based on classification oflanes located ahead in a direction in which the vehicle is traveling androad connection for each lane. This allows the vehicle to appropriatelytravel with autonomous driving assistance based on the specified plannedroute.

A second configuration is as follows.

The autonomous driving assistance system further includes: routepresuming and determining means for determining if a single route can bespecified, based on the road information, as a route that is to be takenby the vehicle on a presumption that the vehicle travels withoutchanging lanes. If the route presuming and determining means determinesthat a single route can be specified, the planned route specifying meansspecifies this route as the planned route.

According to the autonomous driving assistance system having the aboveconfiguration, if a single route can be specified as a route that is tobe taken by the vehicle on the presumption that the vehicle does notchange lanes, this route is specified as a planned route. Accordingly, aroute to be taken by the vehicle can be accurately specified as aplanned route until the vehicle changes lanes. In the case where thevehicle travels with autonomous driving assistance during which lanechanges are not autonomously made, the vehicle basically does not changelanes while traveling. Accordingly, a sufficiently reliable plannedroute can be specified.

A third configuration is as follows.

If there is a branch point ahead in a direction in which the vehicle istraveling, the route presuming and determining means determines if asingle route can be specified, based on the road information, as a routeto be taken by the vehicle.

According to the autonomous driving assistance system having the aboveconfiguration, a planned route to be taken by the vehicle can beaccurately specified based on the information about the line types oflane markings at the branch point and the information about theconnection types of lanes at a position before the branch point.

A fourth configuration is as follows.

The road information about the line types of lane markings includesinformation about a lane marking indicating start of merging or an endof branching of a road, and the road information about the connectiontypes of lanes includes information specifying that each lane is add,continue, end, divide, or merge.

According to the autonomous driving assistance system having the aboveconfiguration, a planned route to be taken by the vehicle can beaccurately specified based on the information specifying how each lanechanges at a position before a branch point.

A fifth configuration is as follows.

If there is at the branch point the lane marking indicating start ofmerging or an end of branching of a road and, as the information aboutthe connection types of lanes, add has been set for a lane next to thelane marking indicating start of merging or an end of branching of aroad, and, as the information about the connection types of lanes, addhas been set for every lane located either on the right or on the leftof the lane for which add has been set, the route presuming anddetermining means determines that a lane in which the vehicle istraveling does not branch at the branch point and another lane is addedat the branch point, and determines that a single route can be specifiedas a route to be taken by the vehicle.

According to the autonomous driving assistance system having the aboveconfiguration, a planned route to be taken by the vehicle can bespecified by using the “line types of lane markings” and the “connectiontypes of lanes.”

A sixth configuration is as follows.

The autonomous driving assistance system further includes: travelinglane specifying means for specifying a lane in which the vehicle istraveling. If there is at the branch point the lane marking indicatingstart of merging or an end of branching of a road and, as theinformation about the connection types of lanes, add has been set for alane next to the lane marking indicating start of merging or an end ofbranching of a road, and, as the information about the connection typesof lanes, add has been set for a single lane located on the right or onthe left of the lane for which add has been set, and the traveling lanespecifying means has specified a lane in which the vehicle is traveling,and as the information about the connection types of lanes, continue hasbeen set for the lane in which the vehicle is traveling, the routepresuming and determining means determines that the lane in which thevehicle is traveling does not divide but branches at the branch point,and determines that a single route can be specified as a route to betaken by the vehicle.

According to the autonomous driving assistance system having the aboveconfiguration, a planned route to be taken by the vehicle can bespecified by using the “line types of lane markings” and the “connectiontypes of lanes.”

A seventh configuration is as follows.

The autonomous driving assistance system further includes: travelinglane specifying means for specifying a lane in which the vehicle istraveling. If there is at the branch point the lane marking indicatingstart of merging or an end of branching of a road and, as theinformation about the connection types of lanes, information other thanadd has been set for a lane next to the lane marking indicating start ofmerging or an end of branching of a road, and the traveling lanespecifying means has specified a lane in which the vehicle is traveling,and as the information about the connection types of lanes, continue hasbeen set for the lane in which the vehicle is traveling, the routepresuming and determining means determines that the lane in which thevehicle is traveling does not divide but branches at the branch point,and determines that a single route can be specified as a route to betaken by the vehicle.

According to the autonomous driving assistance system having the aboveconfiguration, a planned route to be taken by the vehicle can bespecified by using the “line types of lane markings” and the “connectiontypes of lanes.”

The invention claimed is:
 1. An autonomous driving assistance system fora vehicle, comprising: a processor programmed to: access map informationstored in a database; obtain road information that specifies line typesof lane markings and connection types of lanes from the accessed mapinformation; based on the obtained road information, determine whether asingle route can be specified as a route that is to be taken by thevehicle, the determination being made based on a presumption that thevehicle travels without changing lanes; when the vehicle travels withautonomous driving assistance: if the single route can be specified,specify the single route as a planned route to be taken by the vehicle;and if the single route cannot be specified, specify a route along aroad on which the vehicle is currently traveling as the planned route tobe taken by the vehicle; and execute the autonomous driving assistancefor the vehicle according to the specified planned route.
 2. Theautonomous driving assistance system according to claim 1, wherein theprocessor is programmed to: if there is a branch point ahead in adirection in which the vehicle is traveling, determine if the singleroute can be specified, based on the road information, as a route to betaken by the vehicle.
 3. The autonomous driving assistance systemaccording to claim 1, wherein the road information about the line typesof lane markings includes information about a lane marking indicatingstart of merging or an end of branching of a road; and the roadinformation about the connection types of lanes includes informationspecifying that each lane is “add,” “continue,” “end,” “divide,” or“merge.”
 4. The autonomous driving assistance system according to claim3, wherein the processor is programmed to: if there is at the branchpoint the lane marking indicating start of merging or an end ofbranching of a road and, as the information about the connection typesof lanes, add has been set for a lane next to the lane markingindicating start of merging or an end of branching of a road, and, asthe information about the connection types of lanes, add has been setfor every lane located either on the right or on the left of the lanefor which add has been set, determine that a lane in which the vehicleis traveling does not branch at the branch point and another lane isadded at the branch point, and determine that the single route can bespecified as a route to be taken by the vehicle.
 5. The autonomousdriving assistance system according to claim 3, wherein the processor isprogrammed to: specify a lane in which the vehicle is traveling; and ifthere is at the branch point the lane marking indicating start ofmerging or an end of branching of a road and, as the information aboutthe connection types of lanes, add has been set for a lane next to thelane marking indicating start of merging or an end of branching of aroad, and, as the information about the connection types of lanes, addhas been set for a single lane located on the right or on the left ofthe lane for which add has been set, and a lane in which the vehicle istraveling has been specified, and as the information about theconnection types of lanes, continue has been set for the lane in whichthe vehicle is traveling, determine that the lane in which the vehicleis traveling does not divide but branches at the branch point, anddetermine that the single route can be specified as a route to be takenby the vehicle.
 6. The autonomous driving assistance system according toclaim 3, wherein the processor is programmed to: specify a lane in whichthe vehicle is traveling; and if there is at the branch point the lanemarking indicating start of merging or an end of branching of a roadand, as the information about the connection types of lanes, informationother than add has been set for a lane next to the lane markingindicating start of merging or an end of branching of a road, and t alane in which the vehicle is traveling has been specified, and as theinformation about the connection types of lanes, continue has been setfor the lane in which the vehicle is traveling, determine that the lanein which the vehicle is traveling does not divide but branches at thebranch point, and determine that the single route can be specified as aroute to be taken by the vehicle.
 7. An autonomous driving assistancemethod for a vehicle, comprising the steps of: accessing map informationstored in a database; obtaining road information that specifies linetypes of lane markings and connection types of lanes from the accessedmap information; based on the obtained road information, determiningwhether a single route can be specified as a route that is to be takenby the vehicle, the determination being made based on a presumption thatthe vehicle travels without changing lanes; when the vehicle travelswith autonomous driving assistance: if the single route can bespecified, specifying the single route as a planned route to be taken bythe vehicle; and if the single route cannot be specified, specifying aroute along a road on which the vehicle is currently traveling as theplanned route to be taken by the vehicle; and executing the autonomousdriving assistance for the vehicle according to the specified plannedroute.
 8. A computer-readable storage medium storing acomputer-executable autonomous driving assistance program for a vehiclethat causes a computer to perform the following functions: accessing mapinformation stored in a database; obtaining road information thatspecifies line types of lane markings and connection types of lanes fromthe accessed map information; based on the obtained road information,determining whether a single route can be specified as a route that isto be taken by the vehicle, the determination being made based on apresumption that the vehicle travels without changing lanes; when thevehicle travels with autonomous driving assistance: if the single routecan be specified, specifying the single route as a planned route to betaken by the vehicle; and if the single route cannot be specified,specifying a route along a road on which the vehicle is currentlytraveling as the planned route to be taken by the vehicle; and executingthe autonomous driving assistance for the vehicle according to thespecified planned route.